1. Field
One or more embodiments of the present invention relate to a method, medium, and apparatus for setting an exposure time, and more particularly, to a method, medium, and apparatus for setting an exposure time, in which an input image is divided into one or more regions classified into a number of groups according to image information of the regions, a target value is set based on image information of a number of regions classified into one of the groups, and an exposure time is set for each of the regions based on the target value.
2. Description of the Related Art
With the recent advancements made in Internet technologies and the advent of various types of multimedia data, image information has become one of the most important parts of information that is transmitted over the Internet. Even though the importance of moving images as part of visual information has steadily grown due to the advent of various user-created contents (UCCs), the dependence of visual image on still images is still high. Due to the digitalization of increasing number of photographing devices, image sensors have been widely used in photographing devices. As a result of research conducted on image sensors for the past twenty years, digital cameras nowadays are provided with image sensors with 10 megapixels or more, while camera phones are provided with 5-megapixel cameras. However, there is a limit to achieving high resolution enough to clearly render detailed images. Therefore, research has been conducted to determine ways to expand the dynamic range of image sensors, since image sensors are one of the most important factors that affect human visual perception. Technologies which consider human visual perception focus more on how to provide images that can be better seen by the human eye.
Conventional image sensors used in digital cameras, camera phones or digital camcorders generally have a limited dynamic range of less than 60 dB. Thus, the color and picture quality of images captured by such image sensors are deficient compared to the more sensitive dynamic range of the human vision, which is about 100 dB.
The dynamic range of an image sensor may be increased by using either a hardware-based method or a software-based method. The hardware-based method of increasing the dynamic range of an image sensor includes making physical modifications to the image sensor, e.g., modifying the structure of the image sensor or changing color filters, thus enabling the image sensor to receive as much light as possible with increased sensitivity. In addition, the hardware-based method of increasing the dynamic range of an image sensor can increase the sensitivity of the image sensor so that the image sensor can detect even a small amount of light. However, the hardware-based method of increasing the dynamic range of an image sensor also increases the size and manufacturing cost of the image sensor.
In order to address the problems associated with the hardware-based method of increasing the dynamic range of an image sensor, a method has been suggested that involves capturing two or more images using a conventional image sensor and using different exposure times, and compensating the shortage of information by synthesizing the captured images. However, this method requires the exposure times respectively corresponding to the captured images to have an appropriate difference therebetween. To achieve this appropriate difference in exposure times, it is very important to appropriately set the exposure time.